1. Field of the Invention
The present invention relates to a processing system for increasing the quality of a gear, which can efficiently and economically produce a gear of high quality by sequentially subjecting a gear to shot peening and barreling after tooth-forming by hobbing, shaving or rolling and surface hardening such as heat treatment, carburizing or nitriding, or gear surface grinding, so as to enhance dedendum bending fatigue strength, surface durability and abrasion resistance, thereby increasing load capacity.
The present invention can be applicable to any of various gears fabricated in the conventional processes (for example, a spur gear, a helical gear, a double helical gear, a crossed helical gear, a worm gear and the like), and further, is applicable not only to a normal involute form, but also arbitrary tooth forms (for example, a cycloidal curve, a trochoidal curve, a circular arc and the like).
2. Description of the Related Art
A conventional basic series of processes of fabricating a steel gear, which has been subjected to surface hardening such as carburization hardening, includes three kinds of typical processes described below. Here, there will be omitted shot blasting for the purpose of scaling or deburring after the surface hardening or center hole grinding for the purpose of fixing the gear to a shaft.
(1) Hobbing.fwdarw.surface hardening PA1 (2) Hobbing.fwdarw.shaving or rolling.fwdarw.surface hardening PA1 (3) Hobbing.fwdarw.surface hardening.fwdarw.tooth surface grinding PA1 (4) Hobbing.fwdarw.shaving or rolling.fwdarw.surface hardening.fwdarw.shot peening.fwdarw.barreling PA1 (5) Hobbing.fwdarw.surface hardening.fwdarw.tooth surface grinding.fwdarw.shot.fwdarw.peening.fwdarw.barreling
The series (1) of processes, in which a tooth surface is finished only by hobbing, is used in fabricating a relatively large gear for, e.g., a water gate. The series (2) of processes is used in fabricating a small- or middle-sized gear, which is usually used in a transmission for an automobile. The series (3) of processes is used in fabricating a gear for use in a transmission for a prestige car or a speed changer for general industrial machinery.
Nowadays, after the series (2) or (3) of processes, shot peening may be additionally performed for the purpose of enhancement of dedendum bending fatigue strength of the gear. However, if a dedendum is subjected to shot peening, a tooth surface for power transmission becomes rough, thereby arising a problem from the viewpoint of surface durability.
The inventor of the present invention has found that barreling after shot peening can remarkably improve surface durability. In view of this finding, the inventor has devised a basic series of processes as follows:
However, in the series (4) of processes, the shot peening and the barreling are generally performed independently of each other, thereby arising a problem that efficient production cannot be achieved. Moreover, also in the series (5) of processes, the tooth surface grinding, the shot peening and the barreling are generally performed independently of each other, thereby arising the problem that efficient production cannot be achieved. Furthermore, both a shot peening apparatus and a barreling apparatus are relatively liable to induce environmental pollution, thus arising a problem of an increase in cost of cleaning of working environment by means of a dust collecting apparatus or the like.